1. Field of the Invention
The present invention relates to an apparatus and method for locating mobile terminals, and more particularly to an apparatus and method for locating mobile terminals that works together with a global positioning satellite (GPS) to determine the locations of a number of non-identified mobile terminals positioned in a specific area.
2. Description of the Related Art
FIG. 1 is a schematic diagram showing the configuration of a Universal Mobile Telecommunication System (UMTS) as a general mobile communication system. As shown in this figure, the UMTS includes a Core Network (CN) 110, a plurality of Radio Network Subsystems (RNSs) 120 and 130, and User Equipment (UE) 150.
The CN 110 manages information of UEs 150, and performs mobility management, session management, and call management. The RNS 120 or 130 serves to transfer data received from the CN 110 to users via a wireless or an airwave interface. To this end, the RNS 120 or 130 includes a Radio Network Controller (RNC) 121 or 131, and a plurality of base stations (node B) 123 and 125 or 133 and 135. The RNC 121 or 131 is classified into a serving RNC (SRNC), a drift RNC (DRNC) and a controlling RNC (CRNC) based on its operation. The SNRC is an RNC that manages information of UEs belonging to the RNC, and handles data transmission between the UEs and the CN 110 via an Iu interface. The DRNC is an RNC that intermediates data transmission between a UE belonging to a different RNC and an RNC (for example, an SRNC) to which the UE belongs. The CRNC is an RNC that controls each of the base stations. For example, in FIG. 1, if the RNC 121 manages the information of the UE 150, the RNC 121 is an SRNC of the UE 150, and if the UE 150 moves and communicates data with the RNC 121 via the RNC 131, the RNC 131 is a DRNC of the UE 150. In addition, the RNC 121, which controls the base station (node B) 125 in communication with the UE 150, is a CRNC of the base station 125. In the example of FIG. 1, information and data of the UE 150 is transmitted and received from the CN 110 via the RNC 121 that is an SRNC of the UE 150.
There are various methods for locating UEs in a mobile communication network, those are generally divided into three methods. The first is a cell-based location method in which the location of a UE is determined based on information of a cell located nearest to the UE or based on information of a cell that manages the UE. The second is a network-based location method in which a signal measured between the node B and a UE is used to calculate a Time of Arrival (TOA) or a Time Difference of Arrival (TDOA) based on the intensity of the signal or based on radio wave transfer time thereof and the location of the UE is determined by triangulation using the calculated TOA or TDOA. The third is a GPS-based location method in which the location of a UE is determined using a Global Positioning System (GPS) developed by the US Department of Defense. One particular GPS-based location method, which complements and applies the GPS technology to a mobile communication network, is called Network-Assisted GPS (Network-AGPS).
In the prior art, if a Location Service (LCS) client located external to a network requests location determination of a UE, a preparatory process for locating the UE is first performed, and a signal required to locate the UE is measured, and then the location of the UE is calculated based on the measured signal. In the preparatory process, a privacy indicator for limiting access to personal information or the like of the UE is read and network resources are allocated. Then a location technique is selected according to the performance of the UE and the network and quality of Service (QoS) requested by the LCS client. The location measurement process is performed between the Universal Terrestrial Random Access Network (UTRAN) and the UE. In this process, a location measurement signal, including a signal required to measure the location of the UE, is obtained and then the location of the UE is calculated using the location technique selected in the preparatory process. Here, the UE must be an individual UE whose Mobile Subscriber ISDN number (MSISDN) or International Mobile Subscriber Identity (IMSI) is already known.
FIG. 2 is a signal flow diagram showing a conventional method for locating mobile terminals. The conventional mobile terminal location method will now be described with reference to FIG. 2. First, in step S210 if a client 210 requests a CN 220 to locate a UE 240, the location of the UE 240, which the client 210 desires to know, to locate the UE 240 in step S203, the CN 220 requests a UTRAN 230 to which the UE 240 belongs. Then, in step S205 the UTRAN 230 selects a location method according to the performance of the UE 240, requests the UE 240 to provide location measurement information required for the selected location determination method in step SS207, receives a response to the request from the UE 240 in step SS209. The UTRAN 230 calculates the location of the UE using the received information. Alternatively, in step S211 the UTRAN 230 requests the UE 240 to calculate the location, and in step S215 receives the location calculation result calculated in step SS213 from the UE 240, and then transmits the location calculation result to the client 210 via the CN 220 in steps SS217 and S219. In this manner, the UTRAN 230 informs the CN 220 and the client 210 of the location of the UE 240. Here, as described above, the UE must be an individual UE whose MSISDN or IMSI is already known.
In this conventional method, the location measurement of a UE, which is located in a specific area and the location of which is known on a cell basis, is performed only if the LCS client already knows the identifier (MSISDN or IMSI) of the UE. This means that the conventional method can measure only the locations of UEs connected to a communication network. Thus, the conventional method cannot measure the location of an idle UE, which is located in a specific area but is in an idle state, since the location of the idle UE is not managed by an RNC. If the identifier (MSISDN or IMSI) of the idle UE is known, the location, even of the idle UE, can be determined after approximately locating the UE by performing paging of the idle UE. This indicates that the conventional method can locate the UE only if the identifier (MSISDN or IMSI) of the UE is known.
The conventional location method has an additional problem in that processing time increases proportional to the number of UEs, and individual wireless connections cause inefficient use of wireless resources.
In the prior art, as described above, the location of a mobile terminal is detected only when an identifier of the mobile terminal is known and the mobile terminal permits the provision of its location information. This causes mobile terminal location detection to be restricted when attempting to locate mobile terminals for the purpose of rescue when a disaster or a calamity occurs in a specific area such as a rail station, an airport or a mountain.